千慮一失 [ㄑㄧㄢ ㄌㄩˋ ㄧ ㄕ; qian1 lu:4 yi1 shi1]
  reflect a thousand times and you can still make a mistake (idiom); to err is human
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  千慮一失
  せんりょいっしつ
  せんりょのいっしつ
  noun (common) (futsuumeishi)
  mere slip by someone who is usually very careful
  simple mistake by a wise person
  point overlooked by a cautious person
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